In this blog post, we will explore how Rudolf Diesel utilized high compression ratios and fuel characteristics to revolutionize the diesel engine.
It was in 1892 that German inventor Rudolf Diesel came up with the idea for a new engine and obtained a patent for it. At the time, Europe was undergoing rapid mechanization following the Industrial Revolution and was in need of more efficient and economical power sources. The efficiency of the gasoline engine invented by Nikolaus August Otto in 1876 was not very high, and the efficiency of the widely used steam engine was only 10%, with the added drawback of high operating costs. These technical limitations were hindering industrial development, and the need for a better energy conversion system was growing. Rudolf Diesel’s goal was to create a high-efficiency engine, and his idea was to burn fuel at a much higher compression ratio. His research went beyond simply improving the engine; it redefined the fundamental principles of energy conversion.
Generally, gasoline engines first mix air and fuel in a carburetor, then draw the mixture into the cylinder, compress it, and ignite it with a spark plug to generate power. The problem with this process is that the compression ratio is limited. If too much pressure is applied to the vaporized gasoline, it ignites spontaneously, causing engine knocking.
Knocking is an abnormal explosion that occurs inside the cylinder, which can severely impair engine performance and durability. At this point, Rudolf Diesel recognized the need for a major improvement in the existing engine structure. To increase engine efficiency, he devised a method of first strongly compressing air and then injecting fuel to allow it to ignite naturally.
While it was already widely known that compressing air causes it to heat up, effectively applying this principle to an engine was innovative. The basic principle of the diesel engine is to draw air into the cylinder, compress it strongly using a piston, and then inject fuel into the compressed air to achieve spontaneous ignition. Therefore, diesel engines do not require spark plugs but are equipped with fuel injectors. Additionally, since air and fuel do not mix during the compression process, diesel engines have a compression ratio of approximately 25:1, which is much higher than the 12:1 compression ratio of gasoline engines. A higher compression ratio means higher thermal efficiency, enabling diesel engines to produce more energy with less fuel.
Initially, the invention of the diesel engine did not fully realize its potential. The characteristics of the fuel used are also different. Diesel fuel is much heavier, more viscous, and evaporates more slowly than gasoline. This is because diesel fuel contains much more carbon atoms connected in longer chains than gasoline. Generally, gasoline is a mixture of hydrocarbons with 5 to 10 carbon atoms, while diesel fuel is a mixture of hydrocarbons with 16 to 20 carbon atoms. When high temperatures are applied to hydrocarbons with many carbon atoms, they break down into hydrocarbons with fewer carbon atoms. Additionally, diesel fuel has a higher energy density than gasoline. One gallon of diesel fuel contains approximately 155 million joules of energy, while gasoline contains 132 million joules. These fuel characteristics, combined with the high efficiency of diesel engines, result in better fuel economy compared to gasoline engines.
‘Rudolf Diesel’ believed that diesel engines should be small and economical, but during his lifetime, only large and heavy engines were produced. However, his invention opened new possibilities, and through gradual miniaturization and lightweighting, it evolved into a technology applicable to various fields. Following this, automobile manufacturers began to focus on the strengths of diesel engines and apply them to commercial and passenger vehicles. By the mid-20th century, diesel engines were widely used in trucks, buses, and industrial machinery, and diesel technology continued to improve, evolving into more efficient and environmentally friendly engines.
The durability and economy of diesel engines were particularly popular in commercial vehicles, contributing to the growth of large-scale logistics industries. Additionally, technological advancements in diesel engines have enabled their use in power plants, ships, and trains, making them a crucial power source in modern industry. Diesel engines are inherently more robust and less prone to breakdowns than gasoline engines, are less sensitive to fuel quality, and offer superior fuel economy, solidifying their position as the engine of choice for automobiles today. Concerns about diesel engine particulate emissions have also been gradually addressed through advancements in filter technology. Additionally, the development of alternative fuels such as biodiesel has opened up possibilities for further reducing the environmental impact of diesel engines.
The development of the diesel engine has had a profound impact on society and the economy as a whole, transcending mere technological innovation. The legacy left by Rudolf Diesel is not merely an invention of an era but an important lesson in sustainable energy use and efficient resource utilization.
